Cellular base station with intelligent call routing

ABSTRACT

A base station communicates with a plurality of mobile stations over a cellular network. In one embodiment, the base station includes a transceiver configured to receive inbound information from the mobile station and transmit outbound information to the mobile station. The transceiver equalizes and decodes the inbound information and encodes the outbound information. The transceiver is coupled to a data bus for communicating the inbound and outbound information with the other elements in the base station. The transceiver is also coupled to a control bus. An trunk module is coupled to the data bus and to a mobile services center. The trunk module communicates inbound and outbound information with the mobile services center. The trunk module is also coupled to the control bus. Finally, a central processor is coupled to the control bus to control the transceiver and the trunk module. A preferred protocol is Global Systems for Mobile Communication (GSM).

RELATED APPLICATIONS

The present application incorporates the following patent applicationsby reference:

U.S. Ser. No. 08/435,709, filed on May 4, 1995; U.S. Ser. No.08/435,838, filed on May 4, 1995; U.S. Ser. No. 08/434,597, filed on May4, 1995; and U.S. Ser. No. 08/434,554, filed on May 4, 1995.

FIELD

The present invention relates to a cellular base station withintelligent call routing. In particular, the present invention is usedin a cellular network to communicate with mobile stations and controlthe information routing to reduce network congestion and improve networkperformance.

BACKGROUND

Cellular communication networks typically employ base transceiverstations that communicate with mobile stations. When a mobile station(MS) initiates a call to the base transceiver station (BTS), it does sowith an identification code. The BTS sends the identification code to abase station controller (BSC) and mobile switching center (MSC) forauthentication. The MSC determines if the identification code matchesone in a valid subscriber registry. Once authenticated, the BTS isauthorized to communicate with the MS and the network places the call.

Ordinarily, this procedure is efficient. For example, when a MS wishesto communicate with a person at home, via land line, the mobiletransmission is routed through the base station, BSC, MSC, public switchtelephone network (PSTN), and then via land line to the person at home.

However, when one MS wishes to communicate with another MS, thecommunication is still required to route through the MSC. This type ofrouting is not efficient because it reserves a portion of valuable BSC,MSC, and sometimes PSTN resources for the call. Moreover, when the basestation employs a transcoder rate adapter (TRAU), a private branchexchange (PBX), or other subsystems, a portion of those resources arealso reserved for the call.

Hence, one limitation of existing cellular communication networks isthat the BTS and BSC must always communicate with the MSC in order toplace a call from one MS to another. Moreover, this routing may requirea rate adaptation even when the two MS are operating at the same rate.

Another limitation of existing cellular communication networks is thatthey employ dedicated hardware that lacks flexibility. For example, theBTS and BSC may be required to route calls to the MSC whether thisrouting is most efficient or not. As another example, these networks mayimpose rate adaptation on all communications to match a standard rate(e.g., 64 Kbps), whether adaptation is necessary or not.

Still another limitation of existing cellular communication networks isthat they lack flexibility to incorporate advanced features such as callrouting in the BTS and BSC. These networks lack the ability to be scaledand modularized, and lack the flexibility to perform multiple tasks.Moreover, since existing communication networks use a great deal ofdedicated hardware, a fault can cause data loss, or even cause thenetwork to malfunction. When a BTS or BSC is broken, the network mustoperate in a reduced capacity, if it can operate at all.

SUMMARY

The present invention relates to a cellular base station withintelligent call routing. In particular, the present invention is usedin a cellular network to communicate with mobile stations and controlthe information routing to reduce network congestion and improve networkperformance. Exemplary embodiments are provided for use with the GlobalSystems for Mobile Communication (GSM) protocol.

A base station communicates with a plurality of mobile stations over acellular network. In one embodiment, the base station includes atransceiver configured to receive inbound information from the mobilestation and transmit outbound information to the mobile station. Thetransceiver equalizes and decodes the inbound information and encodesthe outbound information. The transceiver is coupled to a data bus forcommunicating the inbound and outbound information with the otherelements in the base station. The transceiver is also coupled to acontrol bus. A trunk module is coupled to the data bus and to a mobileswitching center. The trunk module communicates inbound and outboundinformation with the transceiver and the mobile switching center. Thetrunk module is also coupled to the control bus. Finally, a cellularcentral processor is coupled to the control bus to control thetransceiver and the trunk module.

In another embodiment, the base station may include a plurality oftransceivers, cellular central processors, and trunk modules. The basestation architecture is modular and scalable. As a result, the basestation can be modified to perform a variety of tasks and scaled toaccommodate various performance requirements. For example, a lowperformance base station may have only one transceiver, one cellularcentral processor, and one trunk module. A high performance base stationmay have several transceivers, cellular central processors, and trunkmodules.

Advantages of the present invention include modularity, scalability,distributed processing, improved performance, reduced networkcongestion, fault tolerance, and more efficient and cost-effective basestations.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional advantages of the invention will become apparent upon readingthe following detailed description and upon reference to the drawings,in which:

FIG. 1 depicts a cellular network;

FIGS. 2A-D are flow charts showing steps performed to process inboundinformation and outbound information;

FIG. 3 depicts a base transceiver station according to one embodiment ofthe invention;

FIG. 4 depicts a radio frequency (RF) distribution module according toone embodiment of the invention;

FIG. 5 depicts a transceiver (TRX) module according to one embodiment ofthe invention;

FIG. 6 depicts a cellular central processor according to one embodimentof the invention;

FIG. 7 depicts a trunk module according to one embodiment of theinvention;

FIG. 8 depicts a detailed schematic of a trunk module according toanother embodiment of the invention;

FIGS. 9A-C depict a configuration for switching information at sub-64Kbps rate;

FIG. 10 depicts a base transceiver station according to anotherembodiment of the invention;

FIG. 11 depicts a base transceiver station according to anotherembodiment of the invention;

FIG. 12 depicts a base transceiver station according to anotherembodiment of the invention;

FIG. 13 is a table depicting various embodiments of a base stationaccording to the invention;

FIGS. 14A-D are flow charts showing steps performed to process inboundinformation and outbound information; and

FIGS. 15A-D are flow charts showing steps performed to process inboundinformation and outbound information;

DETAILED DESCRIPTION

The present invention relates to a cellular base station having anintelligent routing control switch. In particular, the present inventionis used in a cellular network to communicate with mobile stations andcontrol the information routing to reduce network congestion and improvenetwork performance. Exemplary embodiments are provided for use with theGlobal Systems for Mobile Communication (GSM) protocol.

The exemplary embodiments are described herein with reference tospecific configurations and protocols. Those skilled in the art willappreciate that various changes and modifications can be made to theexemplary embodiments while remaining within the scope of the presentinvention.

For purposes of this description, the term base station (BS) includesthe structure and features present in any of the BTS, BSC, or MSC. Theexemplary embodiments are capable of performing any of these functionsdepending on their individual configuration, as explained below.Further, the term information includes both RF signals and digital wordsthat can represent voice, data, or both.

A first embodiment is described with reference to FIGS. 1 through 3.FIG. 1 depicts a cellular network showing mobile stations (MS) 20communicating with base transceiver stations (BTS) 40. When a MSinitiates a call to BTS 40, it does so with an international mobilesubscriber identification code (IMSI). BTS 40 sends the IMSI to a basestation controller (BSC) 50 and mobile services center (MSC) 60 forauthentication. MSC 60 determines if the IMSI matches one in a visitorlocation registry (VLR) 70. If the IMSI is not found in VLR 70, MSC 60looks into a home location registry (HLR) 80 to try to match the IMSI.If the IMSI is not found in HLR 80, MSC 60 looks out through the publicswitched telephone network (PSTN) 90 to try to match the IMSI in othernetwork HLRs. Once authenticated, BTS 40 is authorized to communicatewith MS 20 and the network places the call.

FIGS. 2A-D show the procedures for BS 30 to communicate with MS 20.These flowcharts are indicative of a separate BTS 40, BSC 50, MSC 60configuration, and show what processing steps are performed in whatlocation. The FIG. 2A flowchart shows inbound information processingbeginning with step 102 where the information is received from the MS.Step 104 involves framing a GSM TDMA word. In step 106, the informationis equalized to compensate for multipath effects. Step 108 decodes theinformation. Step 110 de-interleaves the inbound information. Steps 112and 114 are information transport steps over a trunk module (TM) which,for convenience is hereinafter described by way of example as anexemplary E1 trunk. Step 116 is a TRAU function that is performed onlywhen required, as explained below. Steps 118 and 120 are informationtransport steps over an exemplary E1 trunk. Step 122 is a switching stepthat routes the inbound information to a correct destination. If thedestination is at the BTS, the information can be routed back to the BTSas outbound information (goto FIG. 2C step 152). However, if the inboundinformation is destined for PSTN 90, step 124 is performed to echocancel the information. Then, step 126 sends the inbound informationover an exemplary E1 trunk to an outbound destination.

The FIG. 2B flowchart shows the inbound control signal processing. Thisrepresents the control information necessary to support voice and datacommunication with MS 20. Steps 102 through 110 are the same as those inthe FIG. 2A flowchart. Step 130 involves base station control functionsincluding control of the base station radio and MS power and timing.Step 132 is an Abis function which is a protocol between the BTS andBSC. Steps 112 and 114 are information transport steps over an exemplaryE1 trunk. Step 134 is an Abis function which is a protcol between theBTS and BSC. Step 136 is a radio resource management (RR) procedure.Step 138 is an A function which is a protocol between the BSC and MSC.Steps 118 and 120 are information transport steps over an exemplary E1trunk. Step 140 is an A function which is a protcol between the BSC andMSC. Step 142 can represent a variety of management procedures includingradio resource management (RR), mobility management (MM), call control(CC), supplemental services (SS), and short message service (SMS). Step144 is SS7 protocol processing, which enables cooperative interworkingbetween other elements of the GSM network and the PSTN. Step 126 sendsthe inbound signal information over an exemplary E1 trunk to an outbounddestination.

The FIG. 2C flowchart shows outbound information processing. Step 150receives the outbound information from an exemplary E1 trunk. Step 152is a switching step that routes the outbound information to a correctdestination. Steps 154 and 156 are information transport steps over anexemplary E1 trunk. Step 158 is a TRAU step. Steps 160 and 162 areinformation transport steps over an exemplary E1 trunk. Step 164interleaves the outbound information. Step 166 encodes the outboundinformation. Steps 168 places the outbound information into TDMA frames.Step 170 transmits the outbound information to MS 20.

The FIG. 2D flowchart shows the outbound signal path processing. Step150 receives the outbound information from an exemplary E1 trunk. Step172 is a SS7 protocol processing, which enables cooperative interworkingbetween other elements of the GSM network and the PSTN. Step 174 canrepresent a variety of management procedures including radio resourcemanagement, mobility management, call control, supplemental services,and short message service. Step 176 is an A function which is a protocolbetween the MSC and BSC. Steps 154 and 156 are information transportsteps over an exemplary E1 trunk. Step 178 is an A function which is aprotcol between the MSC and BSC. Step 180 is a radio resource managementprocedure. Step 182 is an Abis function which is a protcol between theBSC and BTS. Steps 160 and 162 are information transport steps over anexemplary E1 trunk. Step 184 is an Abis function which is a protcolbetween the BSC and BTS. Step 186 involves base station controlfunctions including control of the radio and MS power and timing. Step164 interleaves the outbound information. Step 166 encodes the outboundinformation. Steps 168 places the outbound information into TDMA frames.Step 170 transmits the outbound information to MS 20.

FIG. 3 depicts an embodiment of a base station that communicates withMSs 20a, 20b and performs the inbound information processing andoutbound information processing. A radio frequency (RF) distributionmodule 210 amplifies and distributes inbound information to eachtransceiver (TRX) 250a-c. Each TRX 250 receives the inbound informationand transforms the RF information into GSM TDMA format information. TRX250 then frames, equalizes, decodes, and deinterleaves the inboundinformation, corresponding to steps 104, 106, 108, and 110 of FIGS.2A-B.

TRX 250 is controlled by a cellular central processor (CCPU) 300 via acontrol bus (VME). CCPU 300 schedules all information processing andkeeps track of communication with MS 20. CCPU 300 also controls a trunkmodule (TM) 400 via the VME bus.

TRX 250 then sends the information to TM 400 via a data bus (TDM), whichcontains 16 8 Mbps subbusses. Each TRX module 250a-c can receive on anysubbus and is given a predetermined subbus on which to send informationto TM 400. TM 400 is a sophisticated module that includes a time/spaceswitch, explained below. CCPU 300 controls the operation of TM 400 anddetermines whether TM 400 should perform any rate adaptation, echocancelling, or interface functions, corresponding to steps 116, 122, and124.

The outbound information processing is similarly performed as follows.TM 400 performs, if required, the interface functions and rateadaptation, corresponding to step 158. TM 400 then sends the informationto TRX 250 via TDM bus for interleaving, encoding, framing and RFtransmission, corresponding to steps 164, 166, 168, and 170.

In particular, FIG. 4 depicts RF distribution module 210. Antennae 212,214 are coupled to diplexers 216, 218 respectively. Diplexers 216, 218serve as filters that permit reception and transmission on the sameantenna since the receive frequency is disjoint from the transmitfrequency. Distribution circuits 220, 222 are used to provide fan out ofreceived RF information. One of the circuit 220, 222 outputs are fed toa diversity switch 224. This switch 224 is controlled by downstreamprocessing in order to select antenna 212, 214 with the best reception.In mixer 226, a 13 MHz clock frequency is superimposed on the receivedsignal to synchronize downstream elements such as TRX 250.

FIG. 5 depicts TRX 250. Filter 227 extracts the 13 MHz clock for TRX 250synchronization. A diversity control 228 is coupled to the RFdistribution module 210 to control diversity switch 224. Diversitycontrol 228 monitors the incoming received signal to detect signaldegradation. If, for example, diversity control 228 detects sufficientsignal degradation in antenna 212, it sends a signal to switch 224 in RFdistribution module 210 to select antenna 214. The RF communication andreception aspect is discussed in detail in U.S. Ser. No. 08/434,597.

Once the inbound information is received at TRX 250 and converted to abaseband frequency, a GSM baseband module 230 performs a GMSK procedureto obtain TDMA frame data. GSM baseband module 230 can perform bothinbound demodulation resulting in in-phase and quadrature-phaseinformation as well as outbound modulation resulting in a basebandfrequency. A processor that works well for this purpose is the AnalogDevices AD7002. Then MUX/DMUX 252 directs the inbound information to aplurality of processing paths to distribute the processing load. Thesignal processing U.S. Ser. No. 08/434,554. One example ofdemultiplexing that works well is to send all even TDMA time slots to afirst DSP string 254, 256, and to send all odd TDMA time slots to asecond DSP string 258, 260. However, MUX/DMUX 252 can distribute theinformation to any number of DSP strings. Once DSPs 256, 260 completethe inbound information processing, they send the information to the TDMbus.

For outbound information processing, DSPs 256, 260 receive outboundinformation from the TDM bus. The information is divided among aplurality of processing strings. One example that works well is to sendall even TDMA time slots to a first DSP string 256, 254, and to send allodd TDMA time slots to a second DSP string 260, 258. The processing isperformed in parallel and the resulting outbound information ispresented to MUX/DMUX 252, which multiplexes the time slots to form TDMAframes, sends them to GSM baseband module 230 and then to RFdistribution module 210 for transmission.

While TRX 250 is described for TDMA, any type of modulation, multipleaccess, or other information coding techniques are possible. Forexample, GSM baseband converter 230 can be replaced or supplemented witha converter for performing CDMA, and DSP 254, 256, 258, 260 programmemory can be replaced or supplemented with procedures to perform CDMA.Thus, the modular architecture is capable of performing as any type ofbase station for a variety of different types of networks.

A Real Time Processor (RTP) 262 provisions and controls DSPs 254, 256,258, 260 in order to schedule information processing. RTP 262 alsoperforms power control and measurement preprocessing and link accessprotocols (LAPDm) for information error detection and correction.Moreover, RTP 262 keeps track of inbound information and outboundinformation to further enhance TRX 250 efficiency and permit thecommunication of inbound information and outbound information over theTDM bus.

RTP 262 communicates control information over the VME bus with CCPU 300,and receives instructions from CCPU 300 regarding operating parametersand processing requirements. Included in this control information isbase station radio and MS power and timing information collected by TRX250 as well as other packetized information from the MS. Because RTP 262is incorporated in TRX 250, and since RTP 262 is a dedicated processor,the TRX processing performance is predicable and guaranteed.

RTP 262 is also very useful in microcell configurations where a TRXservice area is small and the signal degrades rapidly. In microcellconfigurations, the signal strength rapidly attenuates with respect todistance. As a result, microcell configurations may require veryfrequent statistics gathering and error checking in order to adequatelymanage the MSs. A conventional radio architecture lacks the processingpower to handle frequent statistics gathering with a number of MSs in amicrocell configuration and may drop the MS, which may have already leftthe service. The invention overcomes the processing hurdle byincorporating RTP 262 in TRX 250 to provide processing that supportsmicrocell configurations and frequent statistics gathering.

RTP 262 serves the goal to distribute processing power and delegateprocessing tasks to where the tasks can be most efficiently performed.In a single TRX configuration, RTP 262 can even perform all thenecessary functions so that a CCPU 300 is not required. Also, asdescribed below, when the number of TRX cards increases, the processingpower scales proportionally. By performing the processing tasks in theTRX, the control traffic is minimized between the TRX and CPU, and theCPU load is not significantly increased with additional TRXs.

FIG. 6 depicts CCPU 300. A VME interface 302 is coupled to the VME busand buffers all communication therewith. A redundancy control 304 iscoupled to interface 302 to monitor interface 302 and to take over ifnecessary. Processor 306 is coupled to interface 302 to communicate overthe VME bus. Processor 306 receives the packetized information from a MSwhen a call is placed. Processor 306 controls the signalling path of thecall and configures TM 400 to accommodate the call switching.Additionally, processor 306 performs many of the housekeeping andscheduling functions required in the BS such as maintaining a record ofactive MSs, MS information rates, call connection information, and otherinformation. Moreover, relating back to FIGS. 2B and 2D, processor 306can provide BCF, RR, MM, SS, CC, or SMS functions if desired (steps 136,142, 174, 180). Clock adjust 308 receives a clock signal and correlatesthe signal with other tracking information, such as data transferclocks, to conform the clock to a uniform standard. CCPU 300 also has avariety of ports for modules such as DRAM 310, flash memory 312, a spareport 314 for IDE, SCSI, or RS232, and ethernet 316.

Some configurations described below have several CCPUs. Benefits ofadditional CCPUs include redundancy, flexibility and increased centralprocessing power. When the base station is coupled to several othernetwork elements, central processing power is useful to coordinateinbound and outbound information, and to control TM 400 switching asdescribed below.

FIGS. 7 and 8 depict TM 400. At the heart of TM 400 is a time/spaceswitch 402, which is coupled to both the TDM bus for data and the VMEbus for control. Time/space switch 402 is capable of routing informationbetween the TDM bus, processor 404, interface framers 410, and DSPs420a-f. Time/space switch 402 is described herein according to itscommunication data rates and switch capabilities. Any device capable ofperforming these functions can be used in the present invention such asthe 3C Ltd. C3280 processor or the Siemens family of digital switchingICs of which PEB 2045 memory time switch is an example.

Time/space switch 402 has many ports as shown in FIG. 8. A PCM inputport is coupled to all 16 TDM subbusses, which can each transfer 8 Mbps.In essence, time/space switch 402 can communicate with up to 16 modulessuch as TRXs, other TMs, or any other type modules attached to the TDMbus. A larger number is possible if time/space switch 402 is configuredto have even more ports and the TDM bus is configured to have even moresubbusses.

Time/space switch 402 supports many of the switching functions describedin U.S. Ser. No. 08/435,709, and U.S. Ser. No. 08/435,838. Moreover,when the base station is configured to perform switching functions, thebase station can perform functions of a cellular PBX, a local loop, orother similar functions.

Processor 404 is coupled to time/space switch 402 via 8 Mbps CPU360Y andCPU360Z input ports, and further coupled to 8 Mbps PathY and PathZoutput ports, as shown. Processor 404 is also coupled to VME bus, asshown in FIG. 7. Processor 404 is provided to perform protocolprocessing. Possible protocols include Abis, A, SS#7, and ISDN. Thisprocessing enables cooperative interworking between other elements ofthe GSM network and the PSTN. Moreover, processor 404 providesdistributed processing that is dedicated to the TM 400 and becomesscaled as the number of TMs increases. Processor 404 also serves as aprotocol engine for TM 400 and helps reduce latency and improveperformance for handling SS#7 signalling. If protocol processing is notrequired, and a CCPU 300 is present in the configuration, then processor404 may be omitted since CCPU 300 includes processor 306 for performinggeneral functions.

Framers 410, 412 are coupled to time/space switch 402 via 2 Mbps framerports T×A and T×B. The 2 Mbps is an E1 interface rate, but can bemodified for any interface rate. Framers 410, 412 are configured tocommunicate with other network elements such as a BTS, BSC, MSC, PBX,PSTN, or others. Since the base station can be configured to perform thefunctions of a BTS, BSC, or MSC, the type of interface may be changed toaccommodate the particular required interface function. For example,framers 410, 412 shown in FIG. 7 can interface with an E1 at 2 Mbps, aT1 at 1.544 Mbps, DS0 at 64 Kbps, or other digital interface.

DSPs 420a-f are coupled to time/space switch via 8 Mbps PathY and pathZoutput ports. A select control store 418 controls what information istransferred to which DSP 420a-f. DSPs 420a-f can perform a variety offunctions including transcode rate adaptation, echo cancelling, or otherspecial functions such as those described below. Once DSPs 420a-fcomplete their respective functions, the information is then deliveredback to time/space switch 402 via pathY and pathZ input ports.

As explained above with reference to FIG. 2A, the required informationprocessing may sometimes include echo cancelling (step 124), transcoderate adaptation TRAU (step 116), or other internetwork functions (IWF).Time/space switch 402 receives control signals from CCPU 300 over theVME bus, instructing time/space switch 402 what to switch or connect.

When echo cancelling, rate adaptation, or some other function isrequired, time/space switch 402 routes the information to a DSP 420 toperform the processing. As shown, there are 6 DSPs 420a-f, however,there may be from zero to any number as required for the processing.Further, the DSPs 420a-f may each have 2 or 4 processor engines such asAT&T DSP1611 or TI TMS320C52 to perform the required processingfunction.

With regard to the TRAU function, the GSM MS communicates compressedvoice at 16 Kbps, while the PSTN DS0 interface is 64 Kbps. A DSP 420modifies the compression to accommodate this rate change. The DSP 420can also accommodate a rate change between any rates such as 8 Kbps, 16Kbps and 64 Kbps.

As mentioned above, information traffic switching at rates below 64 Kbpsis a feature of the invention. Two aspects of the sub-64 Kbpsinformation switching are described. First, a communication is describedthat enables sub-64 Kbps data streams to be assembled into a standardDS0 64 Kbps data stream. To accomplish this aspect, the DSPs 420a-f areemployed to assemble sub-64 Kbps data streams into DS0 data streams tosend to other network elements, and to disassemble DS0 data streams fromother network elements. For example, FIG. 9A shows an 8-bit 64 Kbps DS0data stream 502 containing 4 16 Kbps data streams (W1, W2, W3, W4) andan 8-bit 64 Kbps DS0 data stream 504 containing 8 8 Kbps data streams(W1, W2, W3, W4, W5, W6, W7, W8). This permits either 4 16 Kbps calls or8 8 Kbps calls to be communicated in a single DS0 data stream, whereconventionally only one call is supported. Moreover, the DS0 data streamcan contain a lesser number by padding the data streams withpredetermined bits.

FIG. 9B depicts how DSPs 420a-f can be configured to perform theassembly and disassembly required to read and write the sub-64 Kbps datastreams into 64 Kbps data streams. Each DSP 420 that is instructed toperform the communication has its memory configured with 4 buffers and amap, where the first 4 (M1, M2, M3, M4) are buffers for storing the datastreams and number 5 (M5) is for storing the memory map to direct theDSP function buffer memory mapping. FIG. 9B shows how buffer M1 ismapped to buffer M3 and buffer M2 is mapped to buffer M4, although anymapping can be programmed.

FIG. 9C is a flowchart describing the procedure for mapping TDMinformation into a DS0 64 Kbps data stream. Step 520 is where time/spaceswitch 402 receives time slots information from the TDM bus. Step 522switches desired time slots to selected DSP 420a-f via PcmOut4-7 andPathZ or PathY. In step 524, CCPU 300 sends a map via the VME bus toselected DSP 420a-f that programs the mapping function into M5. Step 526shifts a portion of the time slot information into buffer M1 whileinformation is being shifted out from buffer M4 via PathY or PathZ totime/space switch 402. Step 528 performs the mapping from buffer M1 toM3. Step 530 shifts a portion of the time slot information into bufferM2 while information is being shifted out from buffer M3 via PathY orPathZ to time/space switch 402. Step 532 performs the mapping frombuffer M2 to M4. Step 534 determines whether the DSP 420 shouldcontinue. Under normal circumstances, DSP 420 would continuously processinformation and the loop would continue. However, if the DSP isinstructed to end, step 534 sends the processing to step 536 where theprocessing ends. Thereafter, DSP 420 is free to perform otherprocessing.

Second, to comply with GSM, speech is sampled by MS 20 at 64 Kbps andcompressed to 13.2 Kbps data streams using standard vocoder algorithms.The information is then sent to BTS 40 via RF communication. Eachinbound 13.2 Kbps data stream is received by TRX 250 and typicallypacked into a 16 Kbps data stream and routed within BTS 40. Inconventional equipment, these 16 Kbps data streams are decompressed to64 Kbps and transferred to an MSC where standard 64 Kbps switching isperformed. However, the present invention is capable of intelligentlyrouting calls at 8 Kbps, 16 Kbps, or other rates, thus avoidingunnecessary rate conversions.

This second aspect is apparent when a call is made from a first MS 20ato a second MS 20b within the base station service area. Time/spaceswitch 402 may simply route the inbound information from the first MS20a back out onto the TDM bus as outbound information for the second MS20b. This type of switching is explained below with reference to FIGS.14A-D and 15A-D. Moreover, this type of switching is further explainedin U.S. Ser. No. 08/435,709, and U.S. Ser. No. 08/435,838.

The call routing function can also be performed in a variety of otherways depending on the mobile station communication with a base station.For example, if a first MS 20a and a second MS 20b are communicatingwith a single TRX 250a, and within a single DSP string 254, 256, the DSPstring can receive the inbound data from first MS 20a, and then send itas outbound information to second MS 20b. Since the inbound and outboundinformation is at 13.2 Kbps, and is routed inbound and outbound within asingle DSP string, it does not need to be packed into a 16 Kbps datastream. As another example, if a first MS 20a and a second MS 20b arecommunicating with a single TRX 250a, but with different DSP strings,TRX 250a may receive the inbound data from first MS 20a in one DSPstring, and then send it as outbound information to another DSP stringand then to second MS 20b. Since the inbound and outbound informationare processed by different DSP strings, the information is packed into a16 Kbps data stream for communication between the DSP strings. Moreover,in one case, the first DSP string communicates the information to thesecond DSP string over the TDM bus. As still another example, if a firstMS 20a is communicating with a first TRX 250a and a second MS 20c iscommunicating with a second TRX 250b, first TRX 250a may receive theinbound information and send it via the TDM bus to second TRX 250b,which treats it as outbound information to second MS 20c. Since theinbound and outbound information are processed by different TRXs, theinformation is packed into a 16 Kbps data stream for communicationbetween TRXs. Note that these examples do not send the information to TM400. Note also that these examples do not decompress the information to64 Kbps.

FIG. 10 depicts how the modular and scalable architecture of theinvention is implemented with a TDM bus and a VME bus. RF distributionmodule 210 is coupled to TRX 250. TRX 250 is coupled to both the TDM busand the VME bus. In particular, DSPs 256, 260 are coupled to the TDM busand RTP 262 is coupled to the VME bus. CCPU 300 is coupled to the VMEbus. A clock module 307 is coupled to the TDM bus and generates thereference clock which allows the subsystems to operate in a synchronizedfashion. TM 400 is coupled to both the TDM bus and the VME bus. FIG. 10depicts a one-TRX BTS configuration, which is also depicted in FIG. 11.

FIG. 11 depicts a commercial product that encloses the various basestation components into a chassis. The chassis can operate as a standalone unit, or can be mounted to an equipment rack for deployment in thefield. Moreover, any card can be placed in any slot. It is possible, byremoving all TRXs, to build BSC or MSC configurations using just TM andCCPU cards.

Since the architecture is fully scalable, FIG. 12 depicts a base stationhaving 6 TRXs, 2 CCPUs, and 3 TMs. Any base station configuration andfunction can be accommodated by selecting processing elements fordeployment. For example, FIG. 13 shows various possible functions, suchas BTS, BSC, combined BTS/BSC, MSC, combined BSC/MSC, and combinedBTS/BSC/MSC, that can be achieved with the invention. A configurationhaving a single TRX and single TM is possible when the CCPU functionsare incorporated in the TRX RTP 262 and TM processor 404.

FIGS. 14A-D show the various functional division of inbound informationprocessing and outbound information processing for a combined BTS/BSCand MSC. Those steps common to FIGS. 2A-D have common numbers. Once theinbound information is de-interleaved (step 110), it is sent totime/space switch 402 (step 111). The time/space switch 402 can thenroute the inbound information to one of three places: to the TRAU (step116), to an E1 (step 118), or back to the TDM bus as outboundinformation (goto FIG. 14C step 163). If the switch step 111 routes theinformation to the E1 (step 118), the inbound information is sent to theMSC. Step 120 receives the information at the MSC and switch step 122can then route the inbound information to one of four places: to theTRAU (step 123), to an echo canceler (step 124), to an E1 (step 126), orback to the BTS/BSC as outbound information (goto FIG. 14C step 152).

The FIG. 14B flowchart shows the inbound control signal processing. Notethe Faux Abis step 133. This step is performed to retain the interfacebetween steps 130 and 136 where the information transport steps 112, 114over an exemplary E1 trunk are removed.

With regard to outbound information, step 150 receives information froma foreign network via an E1. The MSC in this case only receives theinformation from the foreign network when the destination MS iscommunicating with a TRX under its control. A switch step 152 can thenroute the information to a TRAU (step 153) or to an E1 (step 160). TheBTS/BSC receives the information on an E1 (step 162) and a switch step163 can then route the information to a TRAU (step 158) or to a TRX thatinterleaves (step 164), encodes (step 166), and frames (step 168) theinformation and sends it to the destination MS via step 170. Note thatboth switch steps 152 and 163 can be initiated from FIG. 14A steps 122and 111 respectively.

The FIG. 14D flowchart shows the outbound control signal processing.Note the Faux Abis step 183. This step is performed to retain theinterface between steps 180 and 186 where the information transportsteps 160, 162 over an exemplary E1 trunk are removed.

FIGS. 15A-D show the various functional division of inbound informationprocessing and outbound information processing for a combinedBTS/BSC/MSC. Those steps common to FIGS. 2A-D have common numbers. Oncethe inbound information is de-interleaved (step 110), it is sent totime/space switch 402 (step 111). The time/space switch 402 can thenroute the inbound information to one of four places: to a TRAU (step116), to an echo canceler (step 124), to an E1 (step 126), or back tothe TDM bus as outbound information (goto FIG. 14C step 152). If theswitch step 111 routes the information to the E1 (step 126), the inboundinformation is sent to a foreign network.

The FIG. 15B flowchart shows the inbound control signal processing. Notethe Faux A step 139. This step is performed to retain the interfacebetween steps 136 and 142 where the information transport steps 118, 120over an exemplary E1 trunk are removed.

With regard to outbound information, step 150 receives information froma foreign network via an E1. The BTS/BSC/MSC in this case only receivesthe information from the foreign network when the destination MS iscommunicating with a TRX under its control. A switch step 152 can thenroute the information to a TRAU (step 158) or to a TRX that interleaves(step 164), encodes (step 166), and frames (step 168) the informationand sends it to the destination MS via step 170. Note that switch step152 can be initiated from FIG. 15A step 111.

The FIG. 15D flowchart shows the outbound control signal processing.Note the Faux A step 177. This step is performed to retain the interfacebetween steps 174 and 180 where the information transport steps 154, 156over an exemplary E1 trunk are removed.

An important feature of the scalable architecture is that when TM cardsare added, the switching ability of the base station increases. Forexample, by configuring a base station with 3 TM modules, as shown inFIG. 12, the base station capacity is increased to 6 E1 output ports.This configuration provides both greater communication capacity to aMSC, as well as greater information switch capacity within the basestation itself, such as between TRX cards.

Advantages of the present invention include modularity, scalability,distributed processing, improved performance, reduced networkcongestion, fault tolerance, and more efficient and cost-effective basestations.

As used herein, when a first element and a second element are coupled,they are related to one another, but need not have a direct path to oneanother. For example, an antenna element may be coupled to a processingelement via a receiver. However, when a first element and second elementare connected, they are required to have a direct path to one another.

Alternative Embodiments

Having disclosed exemplary embodiments and the best mode, modificationsand variations may be made to the disclosed embodiments while remainingwithin the scope of the present invention as defined by the followingclaims.

What is claimed is:
 1. A base station for communicating with a firstmobile station and a second mobile station, said base stationcomprising:a transceiver configured to receive first inbound informationfrom the first mobile station and second inbound information from thesecond mobile station and transmit first outbound information to thefirst mobile station and second outbound information to the secondmobile station; a signal processor coupled to said transceiver and adata bus and configured to equalize and decode said first inboundinformation and said second inbound information and to encode said firstoutbound information and said second outbound information; a transceiverprocessor coupled to said signal processor and said data bus andconfigured to receive control information from said first mobilestation, said second mobile station and said data bus and to controlsaid signal processor, said transceiver processor capable of routingsaid first inbound information from said first mobile station to saiddata bus, routing said first outbound information from said data bus tosaid first mobile station, routing said first inbound information to thesecond mobile station as said second outbound information withoutcommunicating said first inbound information to a foreign network, androuting said second inbound information to the first mobile station assaid first outbound information without communicating said secondinbound information to said foreign network; and a trunk module coupledto said data bus and adapted to couple to said foreign network andconfigured to selectively communicate said first inbound information,said second inbound information, said first outbound information, saidsecond outbound information and said control information with saidforeign network.
 2. A base station for communicating with a first mobilestation and a second mobile station, said base station comprising:afirst transceiver configured to receive first inbound information fromthe first mobile station and transmit first outbound information to thefirst mobile station; a first signal processor coupled to said firsttransceiver and a data bus and configured to equalize and decode saidfirst inbound information and to transmit said first inbound informationto said data bus, and to receive said first outbound information fromsaid data bus and encode said first outbound information; a secondtransceiver configured to receive second inbound information from thesecond mobile station and transmit second outbound information to thesecond mobile station; a second signal processor coupled to said secondtransceiver and said data bus and configured to equalize and decode saidsecond inbound information and to transmit said second inboundinformation to said data bus, and to receive said second outboundinformation from said data bus and encode said second outboundinformation; a central processor coupled to said data bus and configuredto receive control information from said first mobile station and saidsecond mobile station and said data bus and to control said first signalprocessor and said second signal processor in order to provideinstructions to route said first inbound information from said firstmobile station to said data bus, route said first outbound informationfrom said data bus to said first mobile station, route said secondinbound information from said second mobile station to said data bus androute said second outbound information from said data bus to said secondmobile station; and a trunk module coupled to said data bus and adaptedto couple to a foreign network and capable of routing said first inboundinformation from said data bus to said foreign network, routing saidfirst outbound information from said foreign network to said data bus,routing said second inbound information from said data bus to saidforeign network, routing said second outbound information from saidforeign network to said data bus, routing said first inbound informationfrom said data bus back onto said data bus as said second outboundinformation without communicating said first inbound information to saidforeign network, and routing said second inbound information from saiddata bus back onto said data bus as said first outbound informationwithout communicating said second inbound information to said foreignnetwork.
 3. The base station of claim 2, wherein:said trunk module hasan interface processor coupled to said data bus and configured toreceive said first inbound information and said second inboundinformation from said data bus and transmit said first inboundinformation and said second inbound information to a foreign network,and configured to receive said first outbound information and saidsecond outbound information from a foreign network and transmit saidfirst outbound information and said second outbound information to saiddata bus.
 4. The base station of claim 3, wherein:said first inboundinformation includes first inbound voice/data information and firstinbound control information, said first outbound information includesfirst outbound voice/data information and first outbound controlinformation; said second inbound information includes second inboundvoice/data information and second inbound control information, saidsecond outbound information includes second outbound voice/datainformation and second outbound control information; said trunk moduleincludes a time/space switch coupled to said data bus, a plurality ofsignal processors coupled to said time/space switch, and an interfaceframer coupled to said time/space switch; said trunk module includes atranscoder rate adapter to selectively adapt said first inboundvoice/data information, said first outbound voice/data information, saidsecond inbound voice/data information and said second outboundvoice/data information; and said central processor includes a faux Abisconfigured to selectively process said first inbound controlinformation, said first outbound control information, said secondinbound control information and said second outbound controlinformation.
 5. The base station of claim 4, further comprising:acontrol bus coupled to said first transceiver processor, said secondtransceiver processor, said trunk module and said central processor. 6.The base station of claim 5, wherein:said trunk module includes an echocanceler to selectively echo cancel said first inbound voice/datainformation and said second inbound voice/data information; and saidcentral processor includes a faux A configured to selectively processsaid first inbound control information, said first outbound controlinformation, said second inbound control information and said secondoutbound control information.
 7. A base station for processinginformation associated with a first mobile station including firstinbound information having first inbound voice/data information andfirst inbound control information, first outbound information havingfirst outbound voice/data information and first outbound controlinformation, and a second mobile station including second inboundinformation having second inbound voice/data information and secondinbound control information, and second outbound information havingsecond outbound voice/data information and second outbound controlinformation, said base station comprising:a trunk module having a firstterminal adapted to couple to a first foreign network, a second terminaladapted to couple to a second foreign network and an interface processorcoupled to a data bus and a control bus; and wherein:said trunk moduleincludes a time/space switch coupled to said data bus, a plurality ofsignal processors coupled to said time/space switch, and an interfaceframer coupled to said time/space switch; and said trunk module includesa transcoder rate adapter to selectively adapt said first inboundvoice/data information, said first outbound voice/data information, saidsecond inbound voice/data information and said second outboundvoice/data information; and a central processor coupled to said controlbus and configured to selectively process said first inbound controlinformation, said first outbound control information, said secondinbound control information and said second outbound control informationand to control said trunk module; and wherein said trunk module iscapable of selectively routing said first inbound information from saidfirst terminal to said second terminal, routing said first outboundinformation from said second terminal to said first terminal, routingsaid first inbound information from said first terminal back to saidfirst terminal as said second outbound information without communicatingsaid first inbound information to said second foreign network, androuting said second inbound information from said first terminal back tosaid first terminal as first outbound information without communicatingsaid second inbound information to said second foreign network.
 8. Thebase station of claim 7, wherein:said trunk module includes an echocanceler to selectively echo cancel said first inbound voice/datainformation and said second inbound voice/data information; and saidcentral processor includes a faux A configured to selectively processsaid first inbound control information, said first outbound controlinformation, said second inbound control information and said secondoutbound control information.
 9. A base station for processinginformation associated with a first mobile station including firstinbound information having first inbound voice/data information andfirst inbound control information, first outbound information havingfirst outbound voice/data information and first outbound controlinformation, and a second mobile station including second inboundinformation having second inbound voice/data information and secondinbound control information, and second outbound information havingsecond outbound voice/data information and second outbound controlinformation, said base station comprising:a plurality of trunk modules,whereby the base station switch capacity is scaled in proportion to thenumber of trunk modules, and each trunk module having:a terminal adaptedto couple to a foreign network, and an interface processor coupled to adata bus and a control bus a time/space switch coupled to said data bus,a plurality of signal processors coupled to said time/space switch, andan interface framer coupled to said time/space switch; and a transcoderrate adapter to selectively adapt said first inbound voice/datainformation, said first outbound voice/data information, said secondinbound voice/data information and said second outbound voice/datainformation; a central processor coupled to said control bus andconfigured to selectively process said first inbound controlinformation, said first outbound control information, said secondinbound control information and said second outbound control informationand to control said trunk modules; and wherein said trunk modules arecapable of selectively routing said first inbound information from aselected trunk module to said data bus, routing said first outboundinformation from said data bus to said selected trunk module, routingsaid first inbound information from a selected terminal back to saidselected terminal as said second outbound information withoutcommunicating said first inbound information to said foreign network,and routing said second inbound information from said selected terminalback to said selected terminal as first outbound information withoutcommunicating said second inbound information to said foreign network.10. A base station for processing communications associated with a firstmobile station including first inbound information having first inboundvoice/data information and first inbound control information, and firstoutbound information having first outbound voice/data information andfirst outbound control information, and a second mobile stationincluding second inbound information having second inbound voice/datainformation and second inbound control information, and second outboundinformation having second outbound voice/data information and secondoutbound control information, said base station comprising:a trunkmodule having an interface processor coupled to a data bus and a controlbus and capable of routing said first inbound voice/data informationfrom a data bus to a foreign network, routing said second inboundvoice/data information from said data bus to said foreign network,routing said first outbound voice/data information from said foreignnetwork to said data bus, routing said second outbound voice/datainformation from said foreign network to said data bus, routing saidfirst inbound voice/data information from said data bus back onto saiddata bus as said second outbound voice/data information withoutcommunicating said first inbound voice/data information to said foreignnetwork, and routing said second inbound voice/data information fromsaid data bus back into said data bus as said first outbound voice/datainformation without communicating said second inbound voice/datainformation to said foreign network; and wherein:said trunk moduleincludes a time/space switch coupled to said data bus, a plurality ofsignal processors coupled to said time/space switch, and an interfaceframer coupled to said time/space switch; said trunk module includes anecho canceler to selectively echo cancel said first inbound voice/datainformation and said second inbound voice/data information; and saidtrunk module includes a transcoder rate adapter to selectively adaptsaid first inbound voice/data information, said first outboundvoice/data information, said second inbound voice/data information andsaid second outbound voice/data information.
 11. The base station ofclaim 10, wherein:said trunk module is capable of routing said firstcontrol information from said control bus to said foreign network,routing said first outbound control information from said foreignnetwork to said control bus, routing said second control informationfrom said control bus to said foreign network, routing said secondoutbound control information from said foreign network to said controlbus, routing said first inbound control information from said controlbus back onto said control bus as said second outbound controlinformation without communicating said first inbound control informationto said foreign network, and routing said second inbound controlinformation from said control bus back onto said control bus as saidfirst outbound control information without communicating said secondinbound control information to said foreign network.
 12. A base stationchassis capable of being configured into the base station of one ofclaims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 and 11.